The Yule log, cakes, and fir trees derive from German and Celtic customs.
Yule may have derived from the Germanic jol or the Anglo-Saxon geol, which referred to the feast of the winter solstice.
Encyclopedia Brittanica on Christmas
While not known for sure, some sources hold that the pagan Romans sent holly branches as a sign of good wishes at the time of the new year festivals.
Pagans had customarily decorated in winter with evergreens culled from the landscape long before the birth of Christianity. We can still identify with their thought-process, even today: when everything else on the landscape is dead or dormant, evergreens remind us of better times to come -- the return of a green landscape in spring.
An ancient Norse legend relates that Freya, the goddess of love, placed mistletoe in a tree between Heaven and earth, and decided that people who pass underneath it should kiss.
(flourished 4th century, Myra, Lycia, Asia Minor; feast day December 6) Minor saint associated with Christmas. Probably bishop of Myra, he is reputed to have provided dowries for three poor girls to save them from prostitution and to have restored to life three children who had been chopped up by a butcher. He became the patron saint of Russia and Greece, of charitable fraternities and guilds, and of children, sailors, unmarried girls, merchants, and pawnbrokers. After the Reformation his cult disappeared in all the Protestant countries of Europe except Holland, where he was known as Sinterklaas. Dutch colonists brought the tradition to New Amsterdam (now New York City), and English-speaking Americans adopted him as Santa Claus, who is believed to live at the North Pole and to bring gifts to children at Christmas.
Encyclopedia Brittanica on Saint Nicholas
But some may think that gift-giving is Scriptural—as it began with the wise men.
In actual fact, the wise men did not present gifts to Christ because it was his birthday. Rather, they came to present gifts to a King. People from the east never approached the presence of a king without a gift (Clark's Commentary, vol. 5, p. 46). Nowhere in Scripture is there an endorsement to celebrate Christ's birth.
Popular Religious Holidays: Where They Really Came From, The Real Truth Magazine (March 8,2004)